The specific aim of this study is to examine the changes in transcriptional capability and nuclear phosphorylation of proteins that are induced in human fibroblasts (WI38) by the drug Phenytoin. Fibroblasts that have been selected for their high response to Phenytoin will be cultured for the Phenytoin-treated group. The control cultures will be W138 fibroblasts cultured in an identical manner but with no exposure to Phenytoin. Fibroblasts will be selected for high response to Phenytoin by two methods. The first is long term culturing in 1 percent fetal calf serum and 5 ug./ml. Phenytoin. Non-responder fibroblasts do not readily proliferate in such low serum conditions giving a selective advantage to high responder cells. The second method will be to sort WI38 fibroblasts that show properties of high response to Phenytoin by the use of Fluorescence Activated Cell Sorter. Preliminary data have demonstrated some parameters that may be used as the criteria for sorting. The method producing the best cultures of high responding fibroblasts will be used consistently for the described experiments. Phenytoin-treated and control cultures will be examined for the transcriptional capabilities by extracting chromatin from the fibroblasts and transcribing the chromating in vitro with E. Coli RNA polymerase and radioactive precursors. Cultures of the two groups will be grown in the presence of radioactive phosphorus 32p) and nuclear phosphoproteins extracted from isolated fibroblast nuclei. The degree of phosphorylation can be correlated with the specific activity (with respect to (32p) of the protein fractions. Nuclear phosphoproteins from the fibroblasts will be examined by polyacrylamide gel electrophoresis to determine qualitative and quantitative differences in the control versus Phenytoin-treated cultures. The data from these experiments will help design the protocols for future studies using cultured fibroblasts from gingiva of patients exhibiting Phenytoin-induced gingival overgrowth and normal gingival fibroblasts instead of fibroblasts from the WI38 culture line.